Re: [Xen-devel] Hypercall-page initialization

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 7 Feb 2006, at 16:20, Jacob Gorm Hansen wrote:

> I my unprivileged domain builder, I have run into the problem of how
> to setup the hypercall-page. I suppose I can decode the kernel binary
> header to figure out where to put the page, and then memcpy it from
> loader to linux and things will work.
>
> But wouldn't it be better if the hypercall used to populate the page
> was available to the domU, so that its startup-code could call on Xen
> to populate the page? I find the current approach of hardcoding the
> page location in the kernel header pretty ugly.
We can make the hypercall for filling the page one that can be executed 
by unpriv domains (i.e., make it not a dom0_op).
Or if you want to fill it in from within the domU, how about if we did 
something like reserve some space of MSRs for Xen use (e.g., hex 
Bxxxxxxx). Then we could say that, if the guest writes an MFN to a 
particular one of those MSRs, it gets filled with hypercall-page 
goodness. :-)
 -- Keir


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